You want to see if mold grows faster on bread in the shade than on bread in the sun. your experimental variable is 1.mold 2.bread 3.the sun

Actually the sun does change, you are comparing whether the mold will grow faster with and without the sun. so the answer would be the bread, the bread doestn change.

your best option is 5,000 kg

they each offer a fresh glut of resources to the organisms that can arrive and exploit them. as individuals and new species continue to appear, they actively and passively alter the environment. competition for shared resources increases, local abiotic and biotic conditions shift, and the relative abundances of species change accordingly. the process is called ecological succession, and it is one of the earliest and most well-known concepts in ecology.